Both No4's and No1's have been manufactured in 7.62 for military and police issue.
I'm not including the Ishapore 2A and 2A1s in that group. The Indian guns had newly manufactured receivers that used a very high grade steel which were capable of withstanding the pressure of the 7.62 NATO.
Tests with original British and Australian made No. 1 actions resulted in the development of excess headspace within a very few rounds.
The No. 4 rifles were able to withstand a simple conversion to 7.62 NATO as is without the manufacture of new receivers.